1. Field of the Invention
This invention relates to the field of radially expanding tubulars and more specifically to radially expanding tubulars with an expansion assembly having a front anchor assembly.
2. Background of the Invention
Recently, methods and apparatus have been developed for placing tubular strings in a wellbore and then expanding the internal and external diameters of the strings in order to increase a fluid or gas path through the tubular or to line the walls of a wellbore. There are many conventional methods of downhole expansion of tubulars.
Conventional methods include an expansion apparatus that typically includes expander tools, which may be fluid powered and may be run into the wellbore on a work string. The hydraulic expander tools may include an expansion swage, a thruster including multiple pistons capable of providing a sufficient force to propel the expansion swage inside the expandable tubular, and a front and rear anchor. As sufficient pressure is generated, the front anchor may be engaged with the internal wall of the tubular and provide sufficient reaction force for swage propagation inside the tubular. The pressure may then be released, and the anchor may be disengaged from the tubular. The tool may be reset by moving the front anchor forward. This operation is typically repeated multiple times until the front anchor exits the tubular. The rear anchor may then be engaged to provide sufficient reaction force for swage propagation to finish the expansion of the end part of the tubular. However, drawbacks have been encountered with the conventional expansion apparatus. For instance, drawbacks include when the front anchor exits the end portion of the expandable tubular. As pressure is applied, the front anchor being out of the tubular opens-up to the diameter larger than the tubular internal diameter, and the thruster may pull it back inside the tubular against the expansion face of the swage. This may result in damage of the tubular, which may result in failure of the tubular during expansion with the rear anchor and/or damage of the front anchor. Retrieval of the tool may then be problematic.
Consequently, there is a need for an improved method and apparatus for radially expanding tubulars in a wellbore.